Omnidirectional antenna having circumferentially spaced radiators with orthogonal polarization

ABSTRACT

In an omnidirectional antenna of the type including plural individual radiators arranged around the circumferential periphery of a preferably cylindrical body whose diameter is large relative to the operating wave length of the antenna, the respective polarization directions of peripherally adjacent individual radiators are perpendicular to each other. The radiation patterns of the individual radiators overlap in the range of their respective half powers (3db-points). The antenna has a circular radiation characteristic formed by simple addition of the radiation patterns of the individual radiators.

United States Patent Inventor Karl Koob Munich, Germany Appl. No.761,198 Filed Sept. 20, 1968 Patented July 20, 1971 Assignee BolkowGesellschait mit beschrankter lrlaitung Ottobrunn, near Munich, GermanyPriority Sept 22, 1967 Germany P 15 91 008.4

OMNIDIRECTIONAL ANTENNA HAVING CIRCUMFERENTIALLY SPACED RADIATORS WITI'IORTIIOGONAL POLARIZATION 5 Claims, 4 Drawing Figs.

US. Cl 343/705, 343/D1G. 3, 343/799, 343/895 Int. Cl 1101:; 1/28 FieldotSearch 343/705,

708, 756, 797, 778, 895, DIG. 3, 799

[56] References Cited UNITED STATES PATENTS 2,512,137 6/1950 Buchwalteret al. 343/799 3,188,640 6/1965 Simon et a1. 343/705 3,192,529 6/1965Chatelain 343/708 3,438,038 4/1969 Marston 343/778 Primary Examiner--EliLieberman Attorney-McGlew and Toren ABSTRACT: In an omnidirectionalantenna of the type in-' cluding plural individual radiators arrangedaround the circumferential periphery of a preferably cylindrical bodywhose diameter is large relative to the operating wave length of theantenna, the respective polarization directions of peripherally adjacentindividual radiators are perpendicular to each other. The radiationpatterns of the individual radiators overlap in the range of theirrespective half powers (3db-points). The antenna has a circularradiation characteristic formed by simple addition of the radiationpatterns of the individual radiators.

PATENTEDJULPOISYE SHEET 1 OF 2 INVENTOR y Karl Koob 7Www/ M ATTORNEYSPATENTEUJULZOIB?! 3,594,802

SHEET 2 OF 2 Fig. 4

INVENTOR By KCII'l KOOb IWMVTJQ ATTORNEYS OMNIDIRECTIONAL ANTENNA HAVINGCIRCUMFERENTIALLY SPACED RADIATORS WITI'I ORTIIOGONAL POLARIZATIONBACKGROUND OF THE INVENTION Omnidirectional antennae of the mentionedtype are known and are required, for example, in aviation and spaceflight, to communicate by signals with a missile rotating about itslongitudinal axis, for example. Such a missile must have an antennawhich, in a plane normal to its longitudinal axis, has a circ ularradiation characteristic.

The construction of such antennae becomes increasingly more difficult,particularly with boosters and satellites of modern space technology.Thus, on the one hand, the diameter of the antenna carrier, such as abooster or a satellite, becomes increasingly larger and larger and, onthe other hand, increasingly shorter operating wave lengths are used formaintaining signal communications with the boosters and satellites. Forexample, the first stage of the Saturn rocket has a diameter of 6.7 m.,and the signal communication required particularly for telemetryoperations is operated with an operating frequency of 2.2 GHz. Thisresults in a ratio of diameter to wave length D/A) of approximately 50.

If only a few individual radiators are arranged on the surface of acylinder whose diameter is large relative to the operating wave length,there result, in the detennining plane for the radiation characteristic,and perpendicular to the cylinder axis, in certain directions, radiationminima which, in each case, are brought about by a phase oppositionoverlapping of the waves emanating from adjacent individual radiators.

To keep the minima in the radiation characteristic of the antenna assmall as possible, the procedure hitherto has been to arrange, on thesurface of such a cylinder, the largest possible number of individualradiators. Thus, for example, the omnidirectional antenna of thesatellite TELSTAR, whose operating frequency is 6.39 Gl-Iz. and whosediameter is 88 cm. (D/)t=l9) consists of a ring of 72 closely positionedhornlike individual radiators. Such an antenna system, consisting of alarge number of individual radiators, has, however, and precisely forapplications in space technology, substantial disadvantages.

Thus, the large number of individual radiators results in a considerableadditional weight and requires a large portion of the space available onthe surface of the satellite. Moreover, uniform distribution of the highfrequency energy through the individual radiators is difficult,dissipative, and achievable only with a considerable expense. Inspite ofthe above, the radiation pattern, in the determining plane, is mostlyonly insufficiently circular.

SUMMARY OF THE INVENTION This invention relates to omnidirectionalantenna of the type including plural individual radiators arranged onthe surface of a preferably cylindrical body whose diameter is largerelative to the operating wave length of the antenna and, moreparticularly, to an improved and simplified omnidirectional antenna ofthis type.

The objective of the invention is to provide an omnidirectional antennawhich, with a large ratio of the diameter of, for example, a cylindricalantenna carrier, to the operating wave length of the antenna, has asnearly as possible an ideal circular radiation characteristic, andwithout the necessity of continuously increasing the number of theindividual radiators with an increasing ratio of diameter to wave lengthwith the attendant disadvantages.

In accordance with the invention, this problem is solved, with severalindividual radiators of an omnidirectional antenna and arranged on thesurface of a preferably cylindrical body whose diameter is largerelative to the operating wave length of the invention, by providingthat the respective polarization directions of peripherally adjacentindividual radiators are perpendicular to each other, and that therespeclive radiation patterns of individual radiators overlap in therange of their respective half powers on 3 db.-points.

With this surprisingly simple improvement in an omnidirectional antennaof the type mentioned, it is assured that the respective polarizationwaves of adjacent individual radiators, and which are normal orperpendicular to each other, cannot influence one another or interferewith one another. The radiating energy of the overlapping radiationpatterns of adjoining individual radiators are added so that anapproximately ideal circular radiation characteristic of the entireantenna system, and regardless of the magnitude of the ratio of thediameter of the carrier to the wave length, is achieved.

If, in accordance with one embodiment of the invention, circularly orelliptically polarized helical radiators are used as the individualradiators are polarized in the opposite sense of rotation.

In accordance with another embodiment of the invention, the individualradiators can be designed as horn radiators or as dipole radiators.

Accordingly, an object of the invention is to provide an improveddirectional antenna of the type including plural individual radiatorsarranged on and around the peripheral surface of a shaped body whosediameter is large relative to the operating wave length of the antenna.

Another object of the invention is to provide such an omnidirectionalantenna in which the respective polarization directions of peripherallyadjacent individual radiators are perpendicular to each other.

A further object of the invention is to provide such an omnidirectionalantenna in which the respective radiation patterns of individualradiators overlap in the range of their respective half powers or 3db.points.

Still another object of the invention is to provide such anomnidirectional antenna in which the radiating energy of the overlappingradiation patterns of adjoining individual radiators add to each otherso that an approximately ideal circular radiation characteristic of theentire antenna system is attained irrespective of the magnitude of theratio of the diameter of the carrier to the wave length.

A further object of the invention is to provide such an omnidirectionalantenna using individual radiators in the form of circularly orelliptically polarized helical radiators with adjoining individualradiators being polarized in the opposite sense of rotation.

Another object of the invention is to provide such an omnidirectionalantenna in which the individual radiators are designed as horn radiatorsor as dipole radiators.

For an understanding of the principles of the invention, reference ismade to the following description of typical embodiments thereof asillustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the Drawings:

FIG. 1 is a perspective view of an antenna system embodying theinvention and utilizing horn radiators;

FIG. 2 is a perspective view of an antenna system embodying theinvention and utilizing dipole radiators;

FIG. 3 is a perspective view of an antenna system embody- I ing theinvention and utilizing helical radiators; and

FIG. 4 is a graphical illustration of the radiation pattern of antennasystems embodying the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS horn radiators are sodesigned or, respectively, fed, that the radiated electromagnetic wavesof respective adjoining hom radiators, such as those of horn radiators 2and 3, are polarized perpendicularly or normal to each other. Thus, andas shown in FIG. 1, horn radiator 2 is polarized in a direction parallelto the axis of cylinder 1 and horn radiator 3 is polarized in adirection parallel to the diameter ofcylinder 1.

The embodiments of the antenna system shown in FIGS. 2 and 3 closelyresemble that of FIG. 1. In FIG. 2, the horn radiators of FIG. 1 arereplaced by individual dipole radiators, such as the dipole radiator 2'which is polarized parallel to a diameter of cylinder 1 and the dipoleradiator 3' which is polarized parallel to the axis of cylinder 1.

In the embodiment of FIG. 3, the individual radiators are helicalradiators, and the respective elliptical polarizations of adjacentradiators have opposite senses of rotation. Thus, for example, thehelical radiator 2 is polarized clockwise and the helical radiator 3" ispolarized counterclockwise. Since each elliptically polarized wave canbe split up into two mutually perpendicular linear polarized waves,polarized helical radiators, which are polarized in the opposite senseof rotation, can also be considered as being radiators which arepolarized perpendicularly to each other.

Since adjacent individual radiators must be polarized perpendicularly toeach other, the number of individual radiators in all of the antennaembodiments can only be an even number. The radiation patterns 6, 7, 8and 9 of the individual radiators, as shown in FIG. 4, must overlap eachother at the respective half powers or 3 db.-points, since the circularradiation characteristic 10 of the overall antenna system, formed as thesun patterns is formed by simple addition of the radiation patterns ofthe individual radiators.

Basically, any even number of individual radiators is suitable forforming an antenna system embodying the invention.

Antenna embodying 2, 4 and 6 individual radiators are of specialinterest since an antenna system with too large a number ofindividualradiators would have part of the disadvantages of known antenna of thistype. For the half power width Act of the radiation patterns of theindividual radiators, there results, depending on the number n ofindividual radiators contemplated on the antenna carrier, the followingvalue: Aer/degrees 360/n.

What I claim is:

1. In an omnidirectional antenna of the type including plural individualradiators arranged on and around the peripheral surface of a shapedaerodynamic vehicle whose diameter is a large multiple of the operatingwave length of the antenna, the improvement comprising an even number ofindividual radiators, with the respective polarization directions of theradiation of peripherally adjacent individual radiators beingperpendicular to each other and the respective radiation patterns of theindividual radiators overlapping each other in the range of theirrespective half powers or 3 db.-points.

2. In an omnidirectional antenna, the improvement claimed in claim 1, inwhich the individual radiators have elliptic polarizations and therespective elliptic polarizations of peripherally adjacent individualradiators are polarized in the opposite sense of rotation.

3. In an omnidirectional antenna, the improvement claimed in claim I, inwhich the individual radiators are horn radiators.

4. In an omnidirectional antenna, the improvement claimed in claim 1, inwhich the individual radiators are dipole radiators.

5. In an omnidirectional antenna, the improvement claimed in claim 2, inwhich the individual radiators are helical radiators.

1. In an omnidirectional antenna of the type including plural individualradiators arranged on and around the peripheral surface of a shapedaerodynamic vehicle whose diameter is a large multiple of the operatingwave length of the antenna, the improvement comprising an even number ofindividual radiators, with the respective polarization directions of theradiation of peripherally adjacent individual radiators beingperpendicular to each otHer and the respective radiation patterns of theindividual radiators overlapping each other in the range of theirrespective half powers or 3 db.-points.
 2. In an omnidirectionalantenna, the improvement claimed in claim 1, in which the individualradiators have elliptic polarizations and the respective ellipticpolarizations of peripherally adjacent individual radiators arepolarized in the opposite sense of rotation.
 3. In an omnidirectionalantenna, the improvement claimed in claim 1, in which the individualradiators are horn radiators.
 4. In an omnidirectional antenna, theimprovement claimed in claim 1, in which the individual radiators aredipole radiators.
 5. In an omnidirectional antenna, the improvementclaimed in claim 2, in which the individual radiators are helicalradiators.